A similar positioning mechanism is known from DE-OS No. 30 24 109 corresponding to U.S. Pat. No. 4,455,543 therein described concerns a control component in a displacement machine (e.g., a gas exchange valve in an internal combustion engine) which is maintained in each of its opened and closed positions by magnetic attraction, whereby the magnets act against a spring sytem. Two solenoids, situated opposite from one another, hold the gas exchange valve in a given operating position; when the solenoids are not excited (energized), the gas exchange valve's anchor plate, upon which the solenoids exert their attractive force, is situated midway between the solenoids.
Upon startup, however, the attractive force of the solenoids, acting against the spring loading, is insufficient to bring the valve to one of the two operating positions with absolute reliability.
DE-OS No. 30 24 109 therefore recommends the provision of an adjusting unit (also in the form of a solenoid in the embodiment shown therein) in addition to the two actuating solenoids which define the two operating positions. When this adjusting solenoid is not energized, the actuator's anchor plate is not situated midway between the two solenoids, but is instead in contact with the solenoid which defines the closed position. Upon being energized, the adjusting solenoid attracts a support which defines the seat of the spring system, whereby the spring system seat and thus the position of equilibrium of the spring system are simultaneously shifted. This new position of equilibrium, caused by adjusting solenoid energization, is selected such that the actuator's anchor plate is situated between the two actuating solenoids.
Upon startup of the mechanism described in DE-OS No. 30 24 109, energizing one of the actuating solenoids, with which the anchor plate is in contact, is followed by energizing the adjusting solenoid, in order to shift the spring system seat which defines the position of equilibrium of the spring system, such that, upon actuating-solenoid energization, the position of the anchor plate is shifted from contact with one actuating solenoid to a central position between the two actuating solenoids.
As the spring system is of relatively stiff construction in order to achieve rapid actuating times, a relatively strong force is required for action against the spring system, leading to large adjusting-solenoid dimensions.
As the space available is limited, particularly for closely spaced valves in multi-cylinder internal combustion engines, there is thus a need in the art for a smaller adjusting solenoid mechanism.